Silver-Catalyzed Decarboxylative Alkynylation of α,α-Difluoroarylacetic Acids with Ethynylbenziodoxolone Reagents

A decarboxylating alkynylation of α,α-difluoroarylacetic acids with ethynylbenziodoxolone reagents is reported. AgNO₃ serves as the catalyst and K₂S₂O₈ as the oxidant. A series of functional groups were tolerated, and moderate to good yields were obtained

Efficient One-Pot Synthesis of Unsymmetrical Gold(I) N-Heterocyclic Carbene Complexes and Their Use as Catalysts

Eleven different gold­(I) complexes of new NHC ligands were prepared in excellent yield, demonstrating the versatility of the new route to NHC complexes. While the influence of electronically different ligands on the synthesis of the catalysts was small, the catalytic activities of the products differed significantly

Saturated Abnormal NHC–Gold(I) Complexes: Synthesis and Catalytic Activity

New saturated abnormal N-heterocyclic carbene complexes of gold­(I) have been prepared by a 1,3-dipolar cycloaddition of an in situ generated azomethine ylide with an isocyanogold­(I) choride. A series of different substituents on the nitrogen atom of the 1,3-dipole are tolerated without problem. Substitutents on a carbon atom of the 1,3-dipole are problematic in the case of the isocyanogold­(I) chlorides; only low yields are obtained. However, the corresponding isocyanogold­(I) iodide shows good reactivity, and these abnormal N-heterocyclic carbenes bear the substituent in a position α to the carbene carbon, as proven by a crystal structure analysis of one of the products. Some of the new saturated abnormal N-heterocyclic carbene complexes were then tested in the gold-catalyzed phenol synthesis; moderate turnover numbers of 252–380 could be reached

Efficient One-Pot Synthesis of Unsymmetrical Gold(I) N-Heterocyclic Carbene Complexes and Their Use as Catalysts

Eleven different gold­(I) complexes of new NHC ligands were prepared in excellent yield, demonstrating the versatility of the new route to NHC complexes. While the influence of electronically different ligands on the synthesis of the catalysts was small, the catalytic activities of the products differed significantly

Gold Meets Rhodium: Tandem One-Pot Synthesis of β‑Disubstituted Ketones via Meyer–Schuster Rearrangement and Asymmetric 1,4-Addition

An asymmetric one-pot tandem Au/Rh-catalyzed synthesis of highly enantioenriched β-disubstituted ketones starting from racemic propargyl alcohols is disclosed. The compatibility of the two metal complexes (Au/Rh) and their orthogonal ligand systems (NHC/diene) in this bimetallic catalytic system is investigated

The Role of Gold Acetylides as a Selectivity Trigger and the Importance of <i>gem</i>-Diaurated Species in the Gold-Catalyzed Hydroarylating-Aromatization of Arene-Diynes

Terminal 1,2-dialkynylarenes undergo an unexpected cyclization hydroarylation reaction toward naphthalene derivatives in benzene as the solvent. The regioselectivity of the reaction can be controlled by careful catalyst tuning. Also, the preparation of a bench-stable cationic amine complex or simple heterogenization of the catalyst on neutral aluminum oxide, which enables efficient catalyst recycling, was possible. Intensive mechanistic investigations were undertaken, giving new insights into the so-far underestimated role of acetylides in gold chemistry. The gold plays a fascinating dual role serving to both catalyze the reaction and activate the substrate by Au–C-σ bond formation. Evidence of <i>gem</i>-diaurated compounds playing an important part for gold catalysis is also reported

The Role of Gold Acetylides as a Selectivity Trigger and the Importance of <i>gem</i>-Diaurated Species in the Gold-Catalyzed Hydroarylating-Aromatization of Arene-Diynes

Terminal 1,2-dialkynylarenes undergo an unexpected cyclization hydroarylation reaction toward naphthalene derivatives in benzene as the solvent. The regioselectivity of the reaction can be controlled by careful catalyst tuning. Also, the preparation of a bench-stable cationic amine complex or simple heterogenization of the catalyst on neutral aluminum oxide, which enables efficient catalyst recycling, was possible. Intensive mechanistic investigations were undertaken, giving new insights into the so-far underestimated role of acetylides in gold chemistry. The gold plays a fascinating dual role serving to both catalyze the reaction and activate the substrate by Au–C-σ bond formation. Evidence of <i>gem</i>-diaurated compounds playing an important part for gold catalysis is also reported

From Propargylic Amides to Functionalized Oxazoles: Domino Gold Catalysis/Oxidation by Dioxygen

A new, highly efficient, and atom-economic access to a series of functionalized 2,5-disubstituted oxazoles from propargylic amides is reported. A series of propargylic amides were transformed to the corresponding alkylideneoxazolines by a gold­(I) catalyst. The next step was an autoxidation to hydroperoxides bearing the heteroaromatic oxazoles. Experiments addressing the reaction mechanism reveal a radical pathway for this autoxidation process. The hydroperoxides could conveniently be converted to the corresponding alcohols by reduction with sodium borohydride

From Propargylic Amides to Functionalized Oxazoles: Domino Gold Catalysis/Oxidation by Dioxygen

A new, highly efficient, and atom-economic access to a series of functionalized 2,5-disubstituted oxazoles from propargylic amides is reported. A series of propargylic amides were transformed to the corresponding alkylideneoxazolines by a gold­(I) catalyst. The next step was an autoxidation to hydroperoxides bearing the heteroaromatic oxazoles. Experiments addressing the reaction mechanism reveal a radical pathway for this autoxidation process. The hydroperoxides could conveniently be converted to the corresponding alcohols by reduction with sodium borohydride

From Propargylic Amides to Functionalized Oxazoles: Domino Gold Catalysis/Oxidation by Dioxygen

A new, highly efficient, and atom-economic access to a series of functionalized 2,5-disubstituted oxazoles from propargylic amides is reported. A series of propargylic amides were transformed to the corresponding alkylideneoxazolines by a gold­(I) catalyst. The next step was an autoxidation to hydroperoxides bearing the heteroaromatic oxazoles. Experiments addressing the reaction mechanism reveal a radical pathway for this autoxidation process. The hydroperoxides could conveniently be converted to the corresponding alcohols by reduction with sodium borohydride